In the field of cutting devices, circular saws are known for the purpose of cutting slabs and other shapes from blocks or other masses of material such as stone. Since such material inherently is relatively hard, the basic technology employed is different from that used in cutting other materials, such as wood, composition board, paper, or the like, where incisor, severing, shearing, or chipping actions, are adequate. These usually are of little or no practical use with such hard materials. Instead, abrasion of the material being cut, by diamond or other material which is harder and therefore less prone to wear relatively, is frequently used. Thus, circular saws used to cut stone such as granite typically include cutting surfaces in which strong matrix material, such as cobalt or other metal, is provided with pieces of diamond substantially permanently affixed imbedded, encased, or otherwise retained so as to be available at the surface of the matrix to do the actual cutting.
However, particularly in the field of stone cutting, and especially with hard granite and other hard stone materials, there is interest in improving the efficiency, speed, cost effectiveness, and durability of such cutting devices. Normally, they are made from materials such as tungsten carbide, cobalt, bronze, and diamonds, and are costly and difficult to fabricate and tend to operate relatively slowly and to deteriorate rapidly. Further, when deterioration does occur from use, it is difficult, time consuming and costly to correct, often involving the complete removal, reconditioning, resurfacing, and/or other renovation of the blade and/or its cutting surfaces. In addition, increases in the diameter of such blades in order to increase the cutting depth and production rates are accompanied by increases in prices which are disproportionately larger than the corresponding diameter increases, apparently due to manufacturing and/or technical difficulties, market forces, or other operative factors.
Various attempts have been made to address these problems. A current approach is to replace permanent cutting surface material with segments affixed to the circumferential surfaces of the core by means of brazing, welding, adhesives, silver soldering, epoxy or other bonding means. The cutting surfaces of such segments would be made by using embedding, encasing, molding or other means to incorporate diamond particles into a matrix of cast, sintered, pressed or powdered metal, resin or plastic. Usually, the matrix is made from metals such as bronze, cobalt, nickel, tungsten or other material that is susceptible to being bonded by sintering. In this connection, reference is made to Lindblad U.S. Pat. No. 3146561. However, the prior art also demonstrates that retaining such segments in place is a difficult problem, requiring special considerations and imposing particular limitations.
It is known to provide cutting materials in the form of matrix or machined steel inserts for removable affixation in the gullets at the periphery of a circular saw blade core. But such materials inherently are either brittle, or too pliable, and consequently too weak and susceptible to cracking, breaking and otherwise fracturing. Even the basic task of mounting such inserts requires special accommodations to compensate for their comparatively poor structural integrity. In this connection, reference is made to Cofran U.S. Pat. No. 3307242. These same characteristics also limit the physical stresses to which such materials may be exposed in use. Thus, they may limit cutting speeds and pressures, particularly in the context of uses such as cutting stone and other comparatively hard materials.
A related concern is with being able to adapt a circular "center", "disc" or "core" for use effectively in the same manner as would be a large diameter core. In the context of this invention, these terms are intended to be synonymous and to convey the meaning usually attributed to them but, as well, to include saw blades, new or used, albeit normally absent their cutting surfaces. The desirability of being able to do this is reflected in a comparison of the prices currently being charged for circular stone saw blades with diamond cutting surfaces. For example, in 1991, a common diameter core was about 10 ft. which sold for about $13,000, while a core about 11.5 ft. in diameter sold for about $26,000. The disproportionate amount of this increase apparently is a result of several factors, possibly including the more extreme technical difficulties encountered in manufacturing them, the equipment involved, and their greater tendency toward misalignment and vibrating. There are some applications where increased blade diameter is the most practical approach to perform the desired kind of work, as in the matter of cutting larger dimension slabs. Since merely extending the diameter of the cutting surface support, as by adding to the height of the teeth (e.g.), runs afoul of the brittleness and stability limitations referred to above, that expedient alone hasn't yet sufficed.
Some of the special problems attendant to cutting stone and other hard materials are apparent from other prior art references. They reveal that there have been attempts to accommodate the extensive wear usually experienced in such applications by the use of structures which render replacement of the abrading surfaces easier. Some of them have involved brazing, riveting, bolting, or otherwise permanently affixing saw tooth mounts on which abrasive surfaced matrixes might be positioned to the gullet-separated "lands" which, on traditional saw blade cores, become the bases to which are affixed the abrasion impregnated matrixes that do the actual cutting and thus are designated the "teeth". But this, in turn, introduces other difficulties. The abrasive matrixes must be stable positionally, requiring that they have a tight fit when in place. But they also must be adapted to easy removal and affixation, which ordinarily compromises such positional stability, and the inherent brittleness of such abrasive matrixes tends to limit the amount of mechanical stress which they can tolerate. Attempts to circumvent this by using such affixation techniques as brazing or welding the mounts to the core are time consuming and expensive. Further, over the long term, they can derogate the core severely, since repeated and uneven heating tends to introduce internal stress discontinuities and other adverse physical effects which, in turn, produce objectionable misalignments and other undesired ramifications. In an attempt to circumvent this, special mounting techniques have been proposed. In this connection, reference is made to deKok U.S. Pat. Nos. 4641628 and 4517954, and Tanigawa U.S. Pat. No. 4484560. Such proposals, however, do not accommodate themselves to the concurrent objectives of ease of removal of cutting surfaces while maintaining strength and positional stability, of longevity, of increasing the area of cutting surfaces, of improved cooling and cleaning of the cutting surfaces, of increased cutting rates, or of adapting less expensive cores to desired diameter increases.
Accordingly, it is an object of this invention to provide improved means for cutting hard materials.
It is another object of this invention to provide such means in a form wherein the cutting surfaces may be readily installed.
Still another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein the cutting surfaces may be easily removed.
Yet another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein the cutting surfaces may be easily replaced.
Another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein the effective radius of the cutting device may be increased.
Still another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein cooling of the cutting surfaces may be enhanced.
Yet another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein the debris removal from the cutting surfaces is enhanced.
Another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein the cutting surfaces positionally are more stable.
Still another object of this invention is to provide means for achieving one or more of the foregoing objectives wherein straighter and cleaner saw cuts are attainable.